Compositions of human prothrombin and activated factor x for improving hemostasis in the treatment of bleeding disorders

ABSTRACT

Disclosed herein are compositions and methods for improving hemostasis in the treatment of bleeding disorders and reversal of anticoagulant activity. Effective ratios of prothrombin (FII) and activated factor X (FXa) for the treatment of bleeding disorders that are as efficacious as FEIBA®, but require a lower concentration of FII are described herein.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/953,496, filed Mar. 14, 2014, the entire contents ofwhich are hereby incorporated by reference.

FIELD

Disclosed herein are compositions and methods for improving hemostasisin the treatment of bleeding disorders and reversal of anticoagulantactivity.

BACKGROUND

The coagulation cascade by which the human body produces blood clots isthe body's primary mechanism to stop bleeding. Blood clots are producedby platelets sticking together in a fibrin matrix to form a plug at aninjured blood vessel site. The body's inability to form blood clots canlead to excessive bleeding which can be very dangerous. Blood whichcannot clot properly in an individual is often the sign of a bleedingdisorder.

The inability to form blood clots may be due to a deficiency or lack ofclotting factors in the coagulation cascade. For instance, hemophilia A,the most common type of hemophilia, is a largely inherited bleedingdisorder in which there is a Factor VIII (FVIII) deficiency. For aperson with hemophilia A that gets injured, bleeding is not stoppedeasily and requires a longer time to be arrested. The development ofantibodies, also called inhibitors, against FVIII in response to FVIIIreplacement therapy is an additional challenge for treatment ofhemophilia A.

A less common type of hemophilia, hemophilia B, is also a largelyinherited bleeding disorder that results in a Factor IX (FIX) deficiencyand is also known as “Christmas disease.” The development of antibodies,also called inhibitors, against FIX in response to FIX replacementtherapy is an additional challenge for treatment of hemophilia B.

Another bleeding disorder, von Willebrand disease, also an inheritedgenetic disease, is caused by a deficiency or defect in the vonWillebrand factor (vWF), a blood clotting protein. The vWF is criticalin the initial stages of blood clotting as it interacts with theplatelets to form a plug at the site of injury.

Treatment of bleeding disorders usually involves replacing the bloodclotting factor which is either lacking or deficient. The factors caneither be purified from donated human plasma (plasma-derived factors),or made recombinantly (recombinant factors).

Antibodies, also called inhibitors, can develop when an individual witha bleeding disorder is treated with FVIII replacement therapy and thebody recognizes the therapy as a threat instead of treatment. Inresponse to the perceived threat the immune system makes antibodies,also called inhibitors, which attack FVIII. This can be very dangerousas the inhibitors can prevent or inhibit FVIII from controllingbleeding. Therefore, in the case of development of inhibitors againstthe administered clotting factor, bypass therapies have to be applied.Treatment of hemophilia A is complicated by development of FVIIIneutralizing antibodies, occurring in about 30% of patients with severehemophilia A. Similar inhibitory or neutralizing antibody formation canoccur in patients treated with FIX or vWF replacement therapy. Currentlythere are two standard treatment options for hemophilia patients whohave developed inhibitors against FVIII or FIX: monotherapy with FEIBA®(Baxter Healthcare Corporation, Deerfield, Ill.) or recombinant FVIIa.There are other options such as using prothrombin complexes or evenplasma exchange, but they have more side effects and are not asefficacious. FEIBA® (factor eight inhibitor bypassing activity) has beenused for over thirty years in the treatment of patients with hemophilia.It is an integral part of bypass therapy in hemophiliacs withinhibitors, controls bleeding in 93% of episodes, and has a high safetyprofile. Some patients are refractory or non-responsive to monotherapywith FEIBA® or recombinant FVIIa thus, there is a need for improvementof inhibitor therapy in the art. The inventors have identified effectiveratios of human prothrombin (FII) and activated factor X (FXa) for thetreatment of bleeding disorders that are as efficacious as FEIBA®, butrequire a lower amount of FII. FII and FXa can either be recombinant orplasma-derived.

SUMMARY

The present compositions and methods are directed towards improvinghemostasis in the treatment of bleeding disorders and aiding in thereversal of anticoagulant activity.

Effective ratios of prothrombin (FII) and activated factor X (FXa) areherein described to aid in the treatment of bleeding disorders and thereversal of anticoagulant activity. FII and FXa can either berecombinant or plasma-derived.

Certain embodiments include a composition for treating a bleedingdisorder comprising FII and FXa wherein the molar ratio of FXa to FII isless than 1:20,000.

In other embodiments, a composition for treating a bleeding disordercomprises about 0.44 mg/kg of FII and about 826 ng/kg of FXa.Alternatively, the composition can comprise about 0.2 mg/kg to about 1mg/kg of FII and about 560 ng/kg to about 1100 ng/kg of FXa.Alternatively, the composition can comprise about 4.4 mg/kg of FII andabout 275 ng/kg of FXa. Alternatively, the composition can compriseabout 1.2 mg/kg to about 5 mg/kg of FII and about 200 ng/kg to about 540ng/kg of FXa.

In yet other embodiments, a bleeding disorder can include hemophilia A,hemophilia B, von Willebrand disease, congenital hemophilia A withinhibitors or acquired hemophilia A with inhibitory auto antibodies toFVIII, congenital hemophilia B with inhibitors or acquired hemophilia Bwith inhibitory auto antibodies to FIX, blood loss from trauma, FactorVII (FVII) deficiency, Factor V (FV) deficiency, Factor X (FX)deficiency, Factor XI (FXI) deficiency, Factor XIII (FXIII) deficiency,fibrinogen deficiency, prothrombin deficiency, dilutional coagulopathy,thrombocytopenia, blood loss from high-risk surgeries, intracerebralhemorrhage, von Willebrand disease with inhibitors to von Willebrandfactor, or combinations thereof.

Other embodiments include a pharmaceutical composition for treating ableeding disorder comprising FII and FXa wherein the molar ratio of FXato FII is less than 1:20,000 and at least one excipient. FII and FXa caneither be plasma derived or recombinant

In certain embodiments, a pharmaceutical composition can include about0.44 mg/kg of FII and about 826 ng/kg of FXa and at least one excipient.Alternatively, the pharmaceutical composition can comprise about 0.2mg/kg to about 1 mg/kg of FII and about 560 ng/kg to about 1100 ng/kg ofFXa and at least one excipient. Alternatively, the pharmaceuticalcomposition can comprise about 4.4 mg/kg of FII and about 275 ng/kg ofFXa and at least one excipient. Alternatively, the pharmaceuticalcomposition can comprise about 1.2 mg/kg to about 5 mg/kg of FII andabout 200 ng/kg to about 540 ng/kg of FXa and at least one excipient.

In other embodiments, a method of treating a bleeding disorder comprisesadministering a composition comprising FII and FXa wherein the molarratio of FXa to FII is less than 1:20,000 is described. FII and FXa caneither be recombinant or plasma-derived.

Yet further embodiments include a composition for aiding in the reversalof anticoagulant activity comprising FII and FXa wherein the molar ratioof FXa to FII is less than 1:20,000. FII and FXa can either berecombinant or plasma-derived.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating representative thrombin generationprofiles of different combinations of human prothrombin (FII) andactivated factor X (FXa) in FVIII-inhibited human plasma.

FIG. 2 is a diagram illustrating cross-titration of FII and FXa in acalibrated automated thrombography (CAT) assay with FVIII-inhibitedhuman plasma.

FIGS. 3A and 3B illustrate the acute efficacy of different combinationsof FII and FXa in a nail-clip bleeding model in hemophilia-inducedrabbits. FIG. 3A is a schematic overview of the experimental procedure.FIG. 3B is a diagram illustrating relative blood loss following a nailcut which was monitored for 30 minutes before and after intravenousadministration of FII and/or FXa, FEIBA® (positive control), or buffer(negative control). The median for each group is indicated as a blackline.

FIG. 4 is a diagram illustrating the ex vivo analysis of whole bloodsamples from FVIII-inhibited rabbits treated with FII and FXa alone orin combination.

FIG. 5 is a diagram illustrating the CAT analysis of plasma samples fromFVIII-inhibited rabbits treated with FII and FXa alone or incombination.

DETAILED DESCRIPTION

Effective ratios of human prothrombin (FII) and activated factor X (FXa)are herein described to aid in the treatment of bleeding disorders andthe reversal of anticoagulant activity.

Disclosed herein are compositions for treating a bleeding disordercomprising FII and FXa wherein the molar ratio of FXa to FII is lessthan 1:20,000. FII and FXa can either be plasma derived or recombinant.

The production of recombinant proteins such as FII and FXa is well knownin the art. For example, EP 1460131 describes a process for producingrecombinant human blood clotting factors in human cell lines. Further,WO 2005/038019 describes producing high yields of coagulation factorsrecombinantly. The process of isolating coagulation factors from plasmaproducts is also well known in the art. For example, U.S. Pat. No.4,883,598 describes the process for isolating coagulation factors fromblood plasma or plasma products using liquid chromatography.

FEIBA® is a plasma-derived activated prothrombin complex concentrateused to treat bleeding episodes in hemophilic patients with inhibitors.FII and FXa have been identified as the most critical components thatmediate the hemostatic effect of FEIBA®. The molar ratio of FXa and FIIin FEIBA® ranges from 1:20,000-40,000, i.e. 1 U/mL of FEIBA® results inplasma concentrations of 0.035-0.07 nM FXa and 1400 nM FII. The molarratio ranges of FXa to FII in FEIBA® results in a high prothrombinrequirement which is challenging to produce recombinantly. FII and FXare complex proteins with multiple structural domains andpost-translational modifications. Both can be produced recombinantly inmammalian cell lines, e.g. CHO. Factor X needs to be further activatedto FXa for co-formulation with FII in the compositions of the presentembodiments.

Hemophiliac patients “with inhibitors” can mean hemophiliac patientswith antibodies, with neutralizing antibodies, with inhibitoryantibodies or the like. The inhibitors can develop when an individualwith a bleeding disorder is treated with a replacement therapy and thebody recognizes the therapy as a threat instead of treatment.

In the past, recombinant partial prothrombinase has been developed basedon the FXa/FII ratio that is present in FEIBA® to explore the efficacyof this combination of coagulation factors. However, in this approachthe expression and production of high amounts of recombinant FII was thelimiting factor. Studies were performed to identify effective ratios ofhuman FII and FXa that are as active and efficacious as FEIBA®, butrequire a lower amount of FII. Further, exploratory expression studiesby using state-of-the-art expression platforms and clone screeningtechnologies demonstrated technical feasibility of recombinant factor Xand prothrombin generation. State-of-the-art expression system in CHOcells provided high yields at high protein quality and potency for bothfactors. Combination of recombinant FXa and prothrombin may be used asan option for hemophilia inhibitor therapy. An additional benefit of thecompositions of the present embodiments may be decreased risk ofthrombosis, as the FII concentration is lower this may lead to fewerspontaneous clotting events, especially when used in non-hemophilicpatients for anticoagulant reversal.

Surprisingly, it was found that ratios of FII to FXa very different fromthose found in FEIBA® were as effective at controlling bleeding. Incertain embodiments, a composition for treating bleeding disorderscomprises FII and FXa wherein the molar ratio of FXa to FII is less thanabout 1:20,000, less than about 1:19,000, less than about 1:18,000, lessthan about 1:17,000, less than about 1:16,000, less than about 1:15,000,less than about 1:14,000, less than about 1:13,000, less than about1:12,000, less than about 1:11,000, less than about 1:10,000, less thanabout 1:9,000, less than about 1:8,000, less than about 1:7,000, lessthan about 1:6,000, less than about 1:5,000, less than about 1:4,000,less than about 1:3,000, less than about 1:2,000, less than about1:1,000, less than about 1:950, less than about 1:900, less than about1:850, less than about 1:800, less than about 1:750, less than about1:700, less than about 1:650, less than about 1:600, less than about1:550, less than about 1:500, less than about 1:450, less than about1:400, less than about 1:350, less than about 1:300, less than about1:250, less than about 1:200, less than about 1:150, less than about1:100, less than about 1:95, less than about 1:90, less than about 1:85,less than about 1:80, less than about 1:75, less than about 1:70, lessthan about 1:65, less than about 1:60, less than about 1:55, less thanabout 1:50, less than about 1:45, less than about 1:40, less than about1:35, less than about 1:30, less than about 1:25, less than about 1:20,less than about 1:15, less than about 1:10, or less than about 1:5.

In other embodiments, a composition for treating bleeding disorderscomprises FII and FXa wherein the molar ratio of FXa to FII is about1:19,999, about 1:19,500, about 1:18,500, about 1:17,500, about1:16,500, about 1:15,500, about 1:14,500, about 1:13,500, about1:12,500, about 1:11,500, about 1:10,500, about 1:9,500, about 1:8,500,about 1:7,500, about 1:6,500, about 1:5,500, about 1:4,500, about1:3,500, about 1:2,500, about 1:1,500, about 1:950, about 1:900, about1:850, about 1:800, about 1:750, about 1:700, about 1:650, about 1:600,about 1:550, about 1:500, about 1:450, about 1:400, about 1:350, about1:300, about 1:250, about 1:200, about 1:150, about 1:100, about 1:95,about 1:90, about 1:85, about 1:80, about 1:75, about 1:70, about 1:65,about 1:60, about 1:55, about 1:50, about 1:45, about 1:40, about 1:35,about 1:30, about 1:25, about 1:20, about 1:15, about 1:10, or about1:5.

In other embodiments, a composition for treating bleeding disorderscomprises about 0.1 mg/kg of FII and about 800 ng/kg of FXa, about 0.15mg/kg of FII and about 700 ng/kg of FXa, about 0.2 mg/kg of FII andabout 600 ng/kg of FXa, about 0.25 mg/kg of FII and about 500 ng/kg ofFXa, about 0.3 mg/kg of FII and about 400 ng/kg of FXa, about 0.35 mg/kgof FII and about 300 ng/kg of FXa, about 0.4 mg/kg of FII and about 200ng/kg of FXa, about 0.45 mg/kg of FII and about 200 ng/kg of FXa, orabout 0.5 mg/kg of FII and about 100 ng/kg of FXa. In yet otherembodiments, a composition for treating bleeding disorders comprisesabout 0.44 mg/kg of FII and about 826 ng/kg of FXa. In otherembodiments, a composition for treating bleeding disorders comprisesabout 4.4 mg/kg of FII and about 275 ng/kg of FXa.

In certain embodiments, a composition for treating bleeding disorderscomprises about 0.1 mg/kg to about 0.5 mg/kg of FII and about 600 ng/kgto about 1100 ng/kg of FXa, about 0.5 mg/kg to about 1 mg/kg of FII andabout 500 ng/kg to about 1000 ng/kg of FXa, about 1 mg/kg to about 1.5mg/kg of FII and about 450 ng/kg to about 950 ng/kg of FXa, about 2.0mg/kg to about 2.5 mg/kg of FII and about 400 ng/kg to about 900 ng/kgof FXa, about 2.5 mg/kg to about 3.0 mg/kg of FII and about 350 ng/kg toabout 850 ng/kg of FXa, about 3.5 mg/kg to about 4.5 mg/kg of FII andabout 300 ng/kg to about 600 ng/kg of FXa, or about 4.5 mg/kg to about5.5 mg/kg of FII and about 200 ng/kg to about 600 ng/kg of FXa. In otherembodiments, a composition for treating bleeding disorders comprisesabout 0.2 mg/kg to about 1 mg/kg of FII and about 560 ng/kg to about1100 ng/kg of FXa. In yet other embodiments, a composition for treatingbleeding disorders comprises about 1.2 mg/kg to about 5 mg/kg of FII andabout 200 ng/kg to about 540 ng/kg of FXa.

In some embodiments, the FXa is approximately 90% FXaα and 10% FXaβforms. Alternatively the FXa can be approximately 100% FXaα and 0% FXaβforms, approximately 80% FXaα and 20% FXaβ forms, approximately 70% FXaαand 30% FXaβ forms, approximately 60% FXaα and 40% FXaβ forms,approximately 50% FXaα and 50% FXaβ forms, approximately 40% FXaα and60% FXaβ forms, approximately 30% FXaα and 70% FXaβ forms, approximately20% FXaα and 80% FXaβ forms, approximately 10% FXaα and 90% FXaβ forms,or approximately 0% FXaα and 100% FXaβ forms.

Bleeding disorders include, but are not limited to, hemophilia A,hemophilia B, von Willebrand disease, congenital hemophilia A withinhibitors or acquired hemophilia A with inhibitory auto antibodies toFVIII, congenital hemophilia B with inhibitors or acquired hemophilia Bwith inhibitory auto antibodies to FIX, blood loss from trauma, FVIIdeficiency, FV deficiency, FX deficiency, FXI deficiency, FXIIIdeficiency, fibrinogen deficiency, prothrombin deficiency, dilutionalcoagulopathy, thrombocytopenia, blood loss from high-risk surgeries,intracerebral hemorrhage, von Willebrand disease with inhibitors to vonWillebrand factor, or combinations thereof.

Anticoagulants are used to treat and prevent blood clots. Individualswho are at risk at developing a blood clot, or to prevent an existingblood clot from growing, are given an anticoagulant. Those at risk fordeveloping a blood clot include those with atrial fibrillation, amechanical heart valve, endocarditis, mitral stenosis, certain blooddisorders, and those who have had hip replacement surgery or kneereplacement surgery. Sometimes reversal of anticoagulants is necessaryfor example, in situations where there is a high risk of bleeding. Thepharmacological effect of some anticoagulants, for example warfarin, canbe readily reversed by the administration of vitamin K. Some morerecently introduced anticoagulants such as apixaban, betrixaban, andrivaroxaban cannot be readily reversed by the administration of vitaminK. Currently there is no antidote for unwanted bleeding caused by theseanticoagulants which can be quite dangerous. Thus, an additional benefitof the compositions disclosed herein is when used in non-hemophilicpatients for anticoagulant reversal, there are fewer spontaneousclotting events.

Routes of administration for the disclosed compositions include, but arenot limited to, parenteral injection, intravenous injection,subcutaneous injection, and intramuscular injection.

Dosing can be single dosage or cumulative (serial dosing), and can bereadily determined by one skilled in the art. For instance, treatment ofcongenital hemophilia may comprise administration of an effective doseof a composition disclosed herein for an entire lifetime. As anon-limiting example, an effective dose of a composition disclosedherein can be administered once to an individual, e.g., as a singleinjection. Alternatively, treatment of a bleeding disorder may comprisemultiple administrations of an effective dose of a composition disclosedherein carried out over a range of time periods, such as, e.g., daily,once every few days, or weekly. As a non-limiting example, a compositiondisclosed herein can be administered twice or three times weekly to anindividual. The timing of administration can vary from individual toindividual, depending upon such factors as the severity of anindividual's symptoms. For example, an effective dose of a compositiondisclosed herein can be administered to an individual once a day, orevery two to three days, for an indefinite period of time. A person ofordinary skill in the art will recognize that the condition of theindividual can be monitored throughout the course of treatment and thatthe effective amount of a composition disclosed herein that isadministered can be adjusted accordingly. The clinical efficacy can bedescribed by controlling bleeding. Administration can be on demand,prophylactic, pre-operative or peri-operative.

Certain embodiments include a pharmaceutical composition for treatingbleeding disorders comprising plasma-derived FII and FXa wherein themolar ratio of FXa to FII is less than 1:20,000 and at least oneexcipient. Excipients include, but are not limited to, water, NaCl orother salts for isotonicity, 5% dextrose in water, buffered solutionswith a pH of 2-8, trehalose, manitol, or sorbitol as stabilizers,buffers such as phosphate or acetate buffers, tonicity agents such assalts or amino acids, and surfactant polyoxyethylene-sorbitanmonooleate(TWEEN 80). Further the pharmaceutical composition can be lyophilized.

In some embodiments, a pharmaceutical composition for treating bleedingdisorders comprises at least one excipient, FII and FXa, wherein themolar ratio of FXa to FII is less than about 1:20,000, less than about1:19,000, less than about 1:18,000, less than about 1:17,000, less thanabout 1:16,000, less than about 1:15,000, less than about 1:14,000, lessthan about 1:13,000, less than about 1:12,000, less than about 1:11,000,less than about 1:10,000, less than about 1:9,000, less than about1:8,000, less than about 1:7,000, less than about 1:6,000, less thanabout 1:5,000, less than about 1:4,000, less than about 1:3,000, lessthan about 1:2,000, less than about 1:1,000, less than about 1:950, lessthan about 1:900, less than about 1:850, less than about 1:800, lessthan about 1:750, less than about 1:700, less than about 1:650, lessthan about 1:600, less than about 1:550, less than about 1:500, lessthan about 1:450, less than about 1:400, less than about 1:350, lessthan about 1:300, less than about 1:250, less than about 1:200, lessthan about 1:150, less than about 1:100, less than about 1:95, less thanabout 1:90, less than about 1:85, less than about 1:80, less than about1:75, less than about 1:70, less than about 1:65, less than about 1:60,less than about 1:55, less than about 1:50, less than about 1:45, lessthan about 1:40, less than about 1:35, less than about 1:30, less thanabout 1:25, less than about 1:20, less than about 1:15, less than about1:10, or less than about 1:5.

In other embodiments, a pharmaceutical composition for treating bleedingdisorders comprises at least one excipient, FII and FXa, wherein themolar ratio of FXa to FII is about 1:19,999, about 1:19,500, about1:18,500, about 1:17,500, about 1:16,500, about 1:15,500, about1:14,500, about 1:13,500, about 1:12,500, about 1:11,500, about1:10,500, about 1:9,500, about 1:8,500, about 1:7,500, about 1:6,500,about 1:5,500, about 1:4,500, about 1:3,500, about 1:2,500, about1:1,500, about 1:950, about 1:900, about 1:850, about 1:800, about1:750, about 1:700, about 1:650, about 1:600, about 1:550, about 1:500,about 1:450, about 1:400, about 1:350, about 1:300, about 1:250, about1:200, about 1:150, about 1:100, about 1:95, about 1:90, about 1:85,about 1:80, about 1:75, about 1:70, about 1:65, about 1:60, about 1:55,about 1:50, about 1:45, about 1:40, about 1:35, about 1:30, about 1:25,about 1:20, about 1:15, about 1:10, or about 1:5.

In yet other embodiments, a pharmaceutical composition for treatingbleeding disorders comprises at least one excipient and about 0.1 mg/kgof FII and about 800 ng/kg of FXa, about 0.15 mg/kg of FII and about 700ng/kg of FXa, about 0.2 mg/kg of FII and about 600 ng/kg of FXa, about0.25 mg/kg of FII and about 500 ng/kg of FXa, about 0.3 mg/kg of FII andabout 400 ng/kg of FXa, about 0.35 mg/kg of FII and about 300 ng/kg ofFXa, about 0.4 mg/kg of FII and about 200 ng/kg of FXa, about 0.45 mg/kgof FII and about 200 ng/kg of FXa, or about 0.5 mg/kg of FII and about100 ng/kg of FXa. In other embodiments, a composition for treatingbleeding disorders comprises about 0.44 mg/kg of FII and about 826 ng/kgof FXa. In other embodiments, a composition for treating bleedingdisorders comprises about 4.4 mg/kg of FII and about 275 ng/kg of FXa.

In certain embodiments, a pharmaceutical composition for treatingbleeding disorders comprises at least one excipient and about 0.1 mg/kgto about 0.5 mg/kg of FII and about 600 ng/kg to about 1100 ng/kg ofFXa, about 0.5 mg/kg to about 1 mg/kg of FII and about 500 ng/kg toabout 1000 ng/kg of FXa, about 1 mg/kg to about 1.5 mg/kg of FII andabout 450 ng/kg to about 950 ng/kg of FXa, about 2.0 mg/kg to about 2.5mg/kg of FII and about 400 ng/kg to about 900 ng/kg of FXa, about 2.5mg/kg to about 3.0 mg/kg of FII and about 350 ng/kg to about 850 ng/kgof FXa, about 3.5 mg/kg to about 4.5 mg/kg of FII and about 300 ng/kg toabout 600 ng/kg of FXa, or about 4.5 mg/kg to about 5.5 mg/kg of FII andabout 200 ng/kg to about 600 ng/kg of FXa. In other embodiments, acomposition for treating bleeding disorders comprises about 0.2 mg/kg toabout 1 mg/kg of FII and about 560 ng/kg to about 1100 ng/kg of FXa. Inother embodiments, a composition for treating bleeding disorderscomprises about 1.2 mg/kg to about 5 mg/kg of FII and about 200 ng/kg toabout 540 ng/kg of FXa.

To determine the molar ratio of FXa to FII useful in treating bleedingdisorders, a translational in vitro-to-in vivo approach was used. First,combinations were tested in vitro for their procoagulant potential incomparison to FEIBA® using a global hemostatic assay system with humanplasma. Second, selected FII/FXa plasma concentrations were translatedinto doses for hemophilia-induced rabbits and the efficacy assessed inan acute bleeding model.

The experiments for the in vitro and in vivo evaluation of differentratios of human FII and FXa were performed with carefully selectedcommercially available plasma-derived proteins from Enyzme ResearchLaboratories. For the selection, proteins from different suppliers hadbeen tested for purity (Silver staining, Western Blotting), activity(thrombin generation in human and rabbit plasma), concentration andpricing.

Knowing the composition and active components of the multi-componentFEIBA®, a combination of two coagulation factors was generated: humanFII and FXa. A human plasma-based calibrated automated thrombography(CAT) assay was applied to identify FII/FXa combinations at specificratios that had a similar in vitro procoagulant effect inFVIII-inhibited plasma as FEIBA®. Three FII/FXa ratios were selected,translated into preclinical doses and efficacy assessed in a rabbitbleeding model. Three compositions, the first with 100% FII and FXa(same as in FEIBA®), the second with 10% prothrombin and 300% FXa, andFEIBA® showed statistically significant efficacy. The latter dosecontains ˜20-fold less FII and 4-fold more FXa compared to previousstudies. The dose with 25% FII and 200% FXa was not effective. Theobserved hemostatic effect appears to be mediated by neither FII nor FXaalone. In conclusion, the ratio of FII and FXa was adjusted so thatactivity and in vivo efficacy were unaltered and recombinant proteinproduction for a recombinant version of FII/FXa remained feasible.

Example 1 In Vitro Evaluation of FXa/FII Combination in a ThrombinGeneration Assay

The calibrated automated thrombography (CAT) assay has been used tomonitor the pro- and anticoagulant effects of substances in humanplasma. The thrombogram describes the concentration of thrombin inclotting plasma and the CAT is therefore a general physiologic functiontest of the hemostatic system. The assay is based on the measurement offluorescence that is generated by the cleavage of the fluorogenicsubstrate Z-G-G-R-AMC by thrombin over time upon initiation ofcoagulation by Tissue Factor (TF). The assay is performed on aThrombograph™, a 96-well plate fluorometer available from ThermoScientific, and uses a thrombin calibrator that is needed to correct forinner filter effect, donor-to-donor variability in color of plasma,substrate depletion and instrumental differences.

The procoagulant activity of various combinations of plasma-derived FII(140-1400 nM) and FXa (0.035-0.21 nM) was assessed by CAT inFVIII-inhibited plasma. A normal human plasma pool (George KingBiomedical) was treated with 50 Bethesda units (BU)/mL goat anti-FVIIIplasma (Baxter). Corn trypsin inhibitor (CTI, 40 μg/mL, HaematologicTechnologies) was added to inhibit pre-activation by factor XIIa.Clotting was triggered with 1 pM TF+4 μM phospholipids (PL) (PPP LOWreagent, Thrombinoscope BV). Thrombin generation was monitored at 37° C.for 90 min in a Fluoroskan Ascent reader (Thermo Scientific; wavelength390/460 nm) after recalcification. Duplicate measurements were performedfor each sample.

A CAT protocol optimized for rabbit plasma (40 μL/mL CTI, final plasmadilution of 1:3, 0.6 pM TF and 4 μM PL) was used to confirm in spike-instudies that human FII and FXa are also active in rabbit plasma. Thesame CAT protocol was used for the analysis of ex vivo rabbit plasmasamples in the context of the nail clip bleeding study.

The feasibility of reducing the amount of FII within the FII/FXacombination was first tested in a human-plasma based CAT assay. Startingpoint was the FXa:FII ratio as found in FEIBA® (1:20,000), which isequivalent to plasma concentrations of 0.07 nM FXa and 1400 nM FII. Theeffect of decreasing the FII concentration from 1400 nM (100% FII) to140 nM (10% FII) while keeping the FXa concentration constant at 0.14 nM(200%) is shown in FIG. 1. It was observed that 0.14 nM FXa alonecorrected thrombin generation in FVIII-inhibited plasma as well as 1U/mL FEIBA®. The presence of FII increased the endogenous thrombinpotential (ETP) in a dose-dependent manner and resulted in higherthrombin generation than 1 U/mL FEIBA®.

Subsequently, a wider concentration range of FII (105 nM to 1400 nM) andFXa (0.035 to 0.21 nM) was cross-titrated in the CAT assay (FIG. 2). Atarget range for the desired procoagulant activity of FII/FXa wasestablished by testing the effect of 20 different FEIBA® lots at 1 U/mL.The ETP was used as comparative CAT parameter as it showed the mostsignificant change in response to FII/FXa. A few FII/FXa combinationswere identified to lie within the range of FEIBA® activity in correctingthrombin generation in FVIII-inhibited plasma, resulting in 100% to 7.5%prothrombin and 100 to 300% FXa as in FEIBA® (Table 1). A slightdecrease in thrombin generation upon FII reduction can be compensated bya moderate increase in FXa. Three combinations were selected to betested in an in vivo efficacy model in hemophilia A-induced rabbits.

TABLE 1 Summary of FXa:FII molar ratios that reached a procoagulatanteffect (based on ETP values) equivalent to 1 U/mL FEIBA ® in a CAT assaywith FVIII-inhibited human blood. FII FXa (% of amount (% of amount FII(nM) FXa (nM) in FEIBA) in FEIBA) Ratio 1400* 0.07* 100 100  20,000* 7000.07 50 100 10,000 350 0.07 50 100   5000 350 0.14 25 200   2500 1400.14 10 200   1000 140 0.21 10 300   670 105 0.21 7.5 300   500(*indicates the ratio as it is found in FEIBA ®. Combinations markedgrey were selected for in vivo study.

Example 2 In Vivo: Proof of Concept Efficacy in Hemophilia-InducedRabbit Model

The aim of this proof-of-concept study was to assess the efficacy ofthree FII/FXa doses administered together or alone in a nail-clipbleeding model in FVIII-inhibited rabbits (FIG. 3A). The dose withhighest FII amount was 4.4 mg/kg FII+275 ng/kg FXa and is defined as“FEIBA® ratio” and 100% for both FII and FXa. The second dose 1.1 mg/kgFII+551 ng/kg FXa had FII reduced to 25% and FXa increased to 200%. Thethird dose 0.44 mg/kg FII+826 ng/kg FXa had FII reduced to 10% and FXaincreased to 300%. Efficacy was determined for each treatment in termsof reduced blood loss after treatment in comparison to a buffer-onlycontrol group. FEIBA® (75 U/kg) served as a positive control.

Conscious New Zealand white (NZW) rabbits were intravenouslyadministered with 2 mL/kg FVIII inhibitor (17,000 BU/kg) to depleteendogenous FVIII. After approximately 20 mins, the animals wereanesthetized by subcutaneous injection with 5 mg/kg xylazine and 75mg/kg ketamine. Rabbits were laid on a heating pad to preventhypothermia, and the hair on digit II of the right hind limb shaved. Thenail was cut 3 mm from the distal edge of the blood supply matrix 45 minafter application of inhibitor plasma. Blood was then collected for 30min in a tube with saline (room temperature) by immersing the bleedingnail. After this first observation period, the saline tubes wereexchanged to prevent drying of the inflicted wound. Six male NZW rabbitswere used per group. The animals received intravenous treatment withtest or control item. Ten min after application of test or control item,the bleeding nail was inserted in a third tube with saline, and bloodcollected again for 30 min. For each tube, the amount of blood wasmeasured gravimetrically. The experimental procedure is depicted in FIG.3A. The rabbits were killed at the end of the second observation periodby injecting an overdose of pentobarbital.

Blood loss within 30 min before and after application of treatment wassummarized by treatment group using medians, inter-quartile ranges(IQRs), ranges (minimum to maximum), arithmetic means and coefficientsof variation as depicted in FIG. 3B. The efficacious dose of about 826ng/kg of FXa and about 0.44 mg/kg of FII has a 90% reduced FII amountcompared to the FEIBA® ratio. The results demonstrate that lowering theFII amount and slightly increasing FXa is sufficient to correct bleedingin a hemophilia animal model.

Animals were pretreated with FVIII inhibitor to achieve transienthemophilia A, closely mimicking the situation in hemophilic patientswith inhibitors. The efficacy of test and control item was assessedusing a nail-clip bleeding model; thrombelastography and CAT assay wereperformed to gain additional information (see Example 3). In thenail-clip bleeding assay, there was a statistically significantly lowerblood loss with FEIBA® (75 U/kg) than with buffer (p=0.02273) providingstatistical evidence that the complex experimental system was operatingcorrectly. From an exploratory point of view, treatment with FII (4.38mg/kg)+FXa (275 ng/kg) and FII (0.44 mg/kg)+FXa (826 ng/kg) showed astatistically significantly smaller blood loss than buffer (p≦0.01403).In conclusion, it is feasible to reduce the amount of FII in the FII/FXacombination drastically by slightly increasing the amount of FXa withoutlosing the hemostatic efficacy. This would make the commercialproduction of recombinant FII for a recombinant combination of FII/FXaeconomically easier.

Example 3 Ex Vivo Analysis of Rabbit Whole Blood or Plasma byThromboelastography and CAT Assay

Blood samples of FVIII-inhibited rabbits after administration of FEIBA®,FII or FXa alone or in combination, or buffer were analyzed ex vivo bythromboelastography (TEG). Measurements were performed using a TEGhemostasis analyzer 5000 (Haemonetics Corp, USA) at 37° C. Blood wassampled before and 45 min after administration of FVIII-inhibitorplasma, immediately after administration of test or control item, and atthe end of the second bleeding observation period (approximately 40 minafter test item administration). Blood was sampled by puncturing acentral ear artery using a 2-mL syringe (20 gauge needle) filled with0.1 mL sodium citrate and 21 μL CTI (Haematologic Technologies, 3mg/mL). The animals were exsanguinated by cardiac puncture at the end ofthe second bleeding observation period. 1 mL of citrated whole blood(blood:citrate=10:1) was drawn. Each blood sample (320 μL) was mixedwith 20 μL of TF. (0.04 pM final concentration) and re-calcified with 20μL of a 0.2 M CaCl₂ solution in a pre-warmed TEG cuvette at 37° C.Measurement was started immediately and duplicates measured in parallelfor each blood sample. The TEG run was either stopped after all relevantmeasurements were obtained or cancelled after 2 h if no clot formed. TheTEG parameters of clotting time (R-time), speed of clot formation(K-time) rapidity of clot strengthening (angle) and maximum clotfirmness (MA) were recorded.

Ex vivo analysis of whole rabbit blood by TEG (FIG. 4) 5 min aftertreatment with 75 U/kg FEIBA® showed a statistically significantreduction in R-time compared with buffer (p<0.001). The same was truefor all other treatment groups (p<0.001). The effect was still observedat the end of the study, approximately 40 min after test articleadministration, except for the FII alone group where the clotting timewas back at the level of FVIII-inhibited blood. In general, the TEGassay appeared to be very sensitive to FXa. While FXa alone was notefficacious for the reduction of relative blood loss in vivo, the bloodsamples showed significantly reduced R-times ex vivo.

Rabbit plasma samples were also analyzed by CAT analysis. FIG. 5 showsrepresentative thrombin generation profiles for one animal of eachdosing group at all four timepoints. The group dosed with FII alone isnot represented, but had no effect on thrombin generation.Administration of the positive control (75 U/mL FEIBA®) led to thelargest increase in thrombin generation 5 min after treatment. Combinedtreatment of FVIII-inhibited rabbits with plasma-derived human FII andFXa showed a beneficial effect on thrombin generation in rabbit plasmaand reached ETP values that were closer to the normal baseline than theFEIBA® control. A moderate increase in thrombin generation is preferableover massive thrombin generation as this may be an indicator forthrombogenic activity. The most obvious difference between the differentFII/FXa doses in the CAT assay is the high ETP values (area under thecurve) of the thrombin profiles depending on the FII concentration. Thiscan be explained by the additional substrate in the form of prothrombinthat is introduced to the plasma sample, which is quickly activated tothrombin by FXa. Plasmas of animals dosed with FII or FXa administeredalone and the buffer did not affect thrombin generation significantly.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.Recitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is deemedto contain the group as modified thus fulfilling the written descriptionof all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Ofcourse, variations on these described embodiments will become apparentto those of ordinary skill in the art upon reading the foregoingdescription. The inventor expects skilled artisans to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. Each of the above-citedreferences and printed publications are individually incorporated hereinby reference in their entirety.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

We claim:
 1. A composition for treating a bleeding disorder comprisingprothrombin (FII) and activated factor X (FXa) wherein the molar ratioof FXa to FII is less than 1:20,000.
 2. The composition of claim 1,wherein the FII and FXa is plasma derived or recombinant.
 3. Thecomposition of claim 1, wherein the concentration of FII is about 0.44mg/kg and the concentration of FXa is about 826 ng/kg.
 4. Thecomposition of claim 1, wherein the concentration of FII is about 0.2mg/kg to about 1 mg/kg and the concentration of FXa is about 560 ng/kgto about 1100 ng/kg.
 5. The composition of claim 1, wherein theconcentration of FII is about 4.4 mg/kg and the concentration of FXa isabout 275 ng/kg.
 6. The composition of claim 1, wherein theconcentration of FII is about 1.2 mg/kg to about 5 mg/kg and theconcentration of FXa is about 200 ng/kg to about 540 ng/kg.
 7. Thecomposition of claim 1, wherein the bleeding disorder is hemophilia A,hemophilia B, von Willebrand disease, congenital hemophilia A withinhibitors or acquired hemophilia A with inhibitory auto antibodies toFVIII, congenital hemophilia B with inhibitors or acquired hemophilia Bwith inhibitory auto antibodies to FIX, blood loss from trauma, FVIIdeficiency, FV deficiency, FX deficiency, FXI deficiency, FXIIIdeficiency, fibrinogen deficiency, prothrombin deficiency, dilutionalcoagulopathy, thrombocytopenia, blood loss from high-risk surgeries,intracerebral hemorrhage, von Willebrand disease with inhibitors to vonWillebrand factor, or combinations thereof.
 8. The composition of claim1, wherein the composition is administered via parenteral injection,subcutaneous injection, intramuscular injection, or intravenousinjection.
 9. The composition a of claim 1, wherein the composition is apharmaceutical composition.
 10. The composition of claim 9, furthercomprising at least one excipient.
 11. The composition of claim 10,wherein the excipient is selected from a group consisting of water, NaClor other salts for isotonicity, 5% dextrose in water, buffered solutionswith a pH of 2-8, trehalose, manitol, sorbitol, phosphate buffers,acetate buffers, tonicity agents such as salts or amino acids, andsurfactant polyoxyethylene-sorbitanmonooleate (TWEEN 80).
 12. Acomposition for aiding in the reversal of anticoagulant activitycomprising human prothrombin (FII) and activated factor X (FXa) whereinthe molar ratio of FXa to FII is less than 1:20,000.
 13. A method oftreating a bleeding disorder comprising administering a compositionincluding prothrombin (FII) and activated factor X (FXa) wherein themolar ratio of FXa to FII is less than 1:20,000.